Identification of two major ammonia-releasing reactions involved in secondary natto fermentation

• Published in: Bioscience, biotechnology, and biochemistry Vol. 72; no. 7; pp. 1869 - 1876
• Main Authors: Kada, S.(Mizkan Group Corp., Handa, Aichi (Japan)), Yabusaki, M, Kaga, T, Ashida, H, Yoshida, K
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Society for Bioscience, Biotechnology, and Agrochemistry 01.07.2008; Japan Society for Bioscience Biotechnology and Agrochemistry; Oxford University Press
• Subjects: Amino Acids - analysis; AMMONIA; Ammonia - metabolism; AMMONIAC; AMONIACO; BACILLUS SUBTILIS; Biological and medical sciences; Biotechnology; FERMENTACION; FERMENTATION; Fundamental and applied biological sciences. Psychology; GENETIC TRANSFORMATION; GLUTAMATE DEHYDROGENASE; Glutamate Dehydrogenase - metabolism; GLUTAMATE DESHYDROGENASE; GLUTAMATO DESHIDROGENASA; Glutamic Acid - analysis; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; natto; NUCLEOTIDE SEQUENCE; NUTRIENTES; NUTRIENTS; PROTEASAS; PROTEASE; PROTEASES; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE; Soy Foods; Soybean Proteins - metabolism; SUBSTANCE NUTRITIVE; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; Urea - metabolism; UREASA; UREASE; Glutamate dehydrogenase; Enzyme; Bacillus subtilis; natto; Identification; Urease; Bacillaceae; Fermentation; Ammonia; Bacillales; Bacteria; Hydrolases; Oxidoreductases
• ISSN: 0916-8451; 1347-6947
• DOI: 10.1271/bbb.80129

Natto is a traditional Japanese food made from soybeans fermented by strains of Bacillus subtilis natto. It gives off a strong ammonia smell during secondary fermentation, and the biochemical basis for this ammonia production was investigated in this study. When natto was fermented by strain r22, ammonia production was shown to involve degradation of soybean proteins releasing amino acids, and only the glutamate contained in the natto obviously decreased, while the other amino acids increased during secondary fermentation. Strain r22 has two active glutamate dehydrogenase genes, rocG and gudB, and inactivating both genes reduced ammonia production by half, indicating that deamination of glutamate was one of the major ammonia-releasing reactions. In addition, urease encoded by ureABC was found to degrade urea during secondary fermentation. A triple mutant lacking rocG, gudB, and ureC exhibited minimal ammonia production, suggesting that the degradation of urea might be a further ammonia-releasing reaction.